#include<stdio.h>
int main()
{
	float x1,x2,x3,y1,y2,y3,d1,d2,d3,p;
	scanf("%f%f%f%f%f%f",&x1,&y1,&x2,&y2,&x3,&y3);
	d1=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	d2=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
	d3=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
	p=(d1+d2+d3)/2;
	printf("%.2f",sqrt(p*(p-d1)*(p-d2)*(p-d3)));
    return 0;
}

